My now 9yo was suspected of CP & profound deafness at 8mo old. He had lower extremity stiffness, profound developmental delays (at 9mo, he scored between 2-6mo depending on the area--and I realize that's not a 7mo delay in most areas, but it is more than 50% delayed in most areas at that age) and if you dropped a book next to him--he didn't flinch. In retro, when he was VERY young, he wasn't happy unless he was standing (with lots of help, but he wanted to be STANDING). He also had very little attachment to humans at all. I was a SAHM nursing mom and he didn't even notice if I left the room. I thought the concern about CP was a crock until I came home and started tap-tap-tapping at the keyboard only to find that his birth/my pregnancy made him a strong candidate.
He was neither deaf nor had CP. He had A LOT OF PROBLEMS that included seizures (absence seizures--hard to detect but he fell down a lot and a therapist caught an eye flutter that we caught on video and the neuro confirmed), proprioceptive problems, heel-chord stiffness, sensory issues, cognitive delays, immune deficiency, a physical malformation of his heart (very mild, but caused a murmur), and a bunch of stuff. I don't think he knew we were in the room until he was about 15mo (possibly 18mo--don't remember the age, but we both remember the first time it happened :/ ). We started therapy and interventions before your son's age because he was much more severe, but at 20mo, I don't believe he was able to stack yet even after so much therapy and help. At that point, I'm thinking he may have just been able to point to something if asked, but I'm not sure. 18-24mo was a big gain in development for us after a few interventions that clicked for him.
Nine years, lots of research, many nutritional/supplement and therapeutic interventions almost to the day they first uttered that suspected diagnosis to me, he is a bright, social, academically advanced and physically capable (but by no means athletic) kid. Food irritants were a HUGE factor for him and had interfered with his ability to take information in (so that he could develop in many areas) and his ability to function in general. Dietary change put the seizures to bed although we do notice he responds strongly to too much screen time. Therapy was a BIG HELP. We started when he was about 11months old and I think the combination of it all was what got him to where he is. He has a mild Asperger's diagnosis but if you met him, I'm not sure you'd notice. People generally don't. And although he's not really an athletic kid (scrawny and bookish), he has always been in swim lessons and takes a week or two of golf each year. He started running with dad briefly last year and his walk and run are when you see the most noticeable "difference" in him. He just looks gawky and weird.
If my child had cerebral palsy, then we successfully developed his brain to work around the parts that were damaged. I'm not sure what your child's condition is, but I would definitely do what I could to see if various things affect how he functions. It can definitely be exhausting, and I know that after two years--I was pretty well burnt out. But I'm not sorry for it.